The concept of lightweight, inexpensive, corrosion-proof, utility hand pumps for use in removing water from irrigation valve boxes, meter pits, pipe trenches or other places where water can accumulate is known in the art. Typically, all the components of the hand pumps are made from inexpensive plastics or elastomers. A benefit of use of plastic components in the pump is that the plastic is corrosion resistance and allows one to make an inexpensive hand pump that can sustain rough usage in the field. On the other hand a disadvantage of a hand pump made from plastic components is that it is difficult to mate the component parts to each other with the precision found in similar metal pumps. As a result leakage problems can occur in plastic pumps.
Typically, the plastic hand pumps include a plastic handle, which can be used to raise and lower a plastic piston within a plastic pipe. A one-way valve on the bottom of the pipe allows water to enter the bottom of the plastic pipe but prevents backflow out the bottom of the plastic pipe. With each upward stroke the piston lifts the water to a top end of the pipe that includes a plastic end cap having an outlet that directs the water into a side discharge spout, which carries the water away from the pump. The end cap is formed from a resilient polymer plastic material and contains an integral annular sealing member therein that forms a flexible or slide interference fit around the exterior surface of the pump rod shaft to provide a low cost end cap seal for the purposes of preventing leakage between the exterior surface of the pump rod and the annular slide surface of the end cap as the pump rod slides back and forth through the end cap. Unfortunately, the slide interference fit between the flexible end cap seal and the rigid pump rod fails to prevent leakage therepast. Attempts have been made to prevent leakage through the end cap seal through various methods including the use of sealing rings such as “O-rings”. In addition, other types of sealing members have been used in attempt to prevent leakage through the end cap, which have also met with failure. While it is known that effective fluid seals can be made around sliding shafts such systems require precision parts and are costly to manufacture and to use such components in the utility hand pump would defeat the purpose of having a lightweight inexpensive, corrosion proof, utility hand pump. Consequently, while attempts to prevent leakage in these lightweight inexpensive, corrosion-proof, utility pumps have failed the users have tolerated the leakage because of the benefits of having an inexpensive, lightweight, corrosion-proof, utility pump. In addition, because the utility pump is made primarily from plastic components there generally exists lower expectations for plastic pumps than those made from metal parts. Also, since the utility pumps are used in the field of irrigation some leakage can be tolerated even though annoying. All these factors have led to a general acceptance of the leakage as an inherent characteristics of a plastic utility pump. The present invention solves the problem of inhibiting or preventing leakage in the inexpensive, lightweight, corrosion proof utility pumps while avoiding a costly redesign or use of costly pump components.